The histone acetylation and deacetylation of chromatin is one of the critical steps in modulating gene expression, whereas abnormal gene expression is the molecular biological basis of occurrence of tumors and some inherited and metabolic disorders. The acetylation degree of histone is coordinately controlled by histone acetylase (HAT) and histone deacetylase (HDAC). When HDAC are in over expression and recruited by transcription factor, it will result in abnormal inhibition of particular genes, thereby the occurrence of tumors and other diseases. According to the following documents, the activity of HDAC is related to the occurrence of cancers, immune disorders, and some psychiatric and cardiovascular disorders. Experiments show that HDAC inhibitors increase the acetylation level of histone of chromatin, thereby resulting in activated expression of particular genes and the corresponding terminal differentiation of cells and apoptosis of cancer cells. Primary clinical study shows that humans can obtain a high acetylation level of histone safely by inhibiting HDAC activity. Therefore, HDAC has become the latest and hottest target in the research of chemotherapeutic drugs of tumors.